1. Technical Field of the Invention
The present invention relates generally to spark plugs for igniting the air/fuel mixture within a combustion chamber of an engine.
More particularly, the invention relates to a spark plug that has easy-to-recognize identification marks formed thereon, through which the spark plug can be easily differentiated from other spark plugs.
2. Description of the Related Art
Many products, including spark plugs for internal combustion engines, generally have identification marks formed thereon, which serve various purposes.
For example, identification marks may be used to provide information about the manufacturer and the type of product. Identification marks may also be used to indicate the serial number or batch code of the product.
A number of methods have been proposed to apply identification marks to products.
Japanese Utility Model First Publication No. S49-1727 describes a method of applying an identification mark to a spark plug. According to the method, one of the terminal, housing (or metal shell), and insulator of the spark plug is designed to have a specific color that is indicative of the heat range of the spark plug. In other words, an identification mark is applied to the spark plug in the form of color.
However, in the above case, since the number of colors available is limited, it is difficult to provide more information about the spark plug so as to easily identify it among various types of spark plugs.
Japanese Utility Model No. 3078913 describes a ceramic catalyst support that is cylindrical in shape and has identification marks engraved on the outer side surface thereof with a laser beam.
In the above support, the identification marks are formed occupying only a certain angular range, not the whole angular range in the circumferential direction of the support. Consequently, in some cases, it is required to rotate the support to a suitable position where the identification marks can be accurately recognized by a recognition device.
Accordingly, to identify the above support, an additional apparatus (or device) and time is required to perform the task of rotating the support to a suitable position, thus increasing manufacturing cost of the support.